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Histopathological Relationship of Fusarium and Thielaviopsis with Beans. R. E. Pierre, Plant Pathologist, University of the West Indies, Mona, Jamaica, New York 14850, The senior author was formerly Research Associate, Department of Plant Pathology, Cornell University; R. E. Wilkinson, Associate Professor, Department of Plant Pathology, Cornell University, Ithaca, New York 14850. Phytopathology 60:821-824. Accepted for publication 7 December 1969. DOI: 10.1094/Phyto-60-821.

Fusarium solani f. sp. phaseoli and Thielaviopsis basicola were utilized in a comparative histopathological study of four bean lines: Phaseolus coccineus ‘Scarlet Runner’; P. vulgaris (P.I. 203958, also called N203); N203 × (P. vulgaris² × P. coccineus)—F6 (2051-02); and P. vulgaris ‘Red Kidney’. Red Kidney is susceptible to both pathogens, but the other bean lines show various degrees of resistance. The mode of ingress and pattern of development of the pathogens were different, but the early response of the bean lines to either pathogen was essentially similar. Certain differences in host response became evident as infection progressed. There was a rapid accumulation of brown materials in resistant lines in advance of the area invaded by the fungi. Infection of Scarlet Runner at or near soil level by either pathogen resulted in hypertrophy of the cortical cells internal to the lesion, and subsequent formation of a periderm. A protective periderm also developed in N203 and 2051-02, but in these lines, cell division generally began in the endodermal layer. Since the development of hyphae was restricted in resistant lines regardless of the presence or absence of this barrier, periderm formation apparently is of secondary significance as a factor in the resistance of beans to these pathogens.